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What's a similar looking aircraft to this illustration?
There is this crazy picture of a plane or a boat or both...?

This is just a drawing, I know, but if this aircraft does not exist, is there perhaps a similar looking one in reality?

I believe the golden bar/pillar in the right foreground is a palm tree trunk.

It is just a drawing, there is no basis/analog in reality.

I really like the windows in the wings.

Just a random comment:  I was at a RC aircraft show and saw a model based off of your drawing.  That thing was a large-scale model (by my estimate 6 or 7 feet wide) and was awesome!

The airplane depicted is a seaplane which seems to be roughly 70 feet in height. The largest real seaplane in the world seems to be only 40 feet in height: https://en.wikipedia.org/wiki/AVIC_AG600

@TannerSwett The Spruce Goose would dispute that claim, and had a total height of 79 feet. The fuselage height on the H-4 was only 30 feet (your 39 foot is total height, probably closer to 18 for the fuselage only).

I edited the question to make it more relevant and on-topic

I wonder where the fuel is supposed to be stored, if even the wings are occupied by passengers.

Very recent, anachronistic answer: https://www.theguardian.com/world/2017/dec/24/ag600-world-largest-amphibious-aircraft-takes-off-in-china

Given the windows on the leading edge, suggested additional reading: Why are there so few aircraft that had inhabited wings?

is there perhaps a similar looking one in reality?

Not really, however the fictional five-deck flying boat depicted is clearly an extrapolation of flying boats of the first half of the 20th century.
Visually, the Short Empire class is the most similar:

domed cockpit at front of hull
hull chines
four radial engines mounted in-wing with three-blade propellers
conventional empennage

Photo of a Short Empire, Public Domain

Photo of a Short Sunderland, CCASA3.0 Nick.D
The largest all-metal flying boat developed for civilian passenger service was the Saunders-Roe Princess which only had two passenger-decks.

Photo of a Saunders-Roe Princess, Public Domain
The largest flying boat was probably the Hughes H-4 Hercules, popularly known as the Spruce Goose. It was designed for military transport (hence no windows). I believe it would have accomodated both troops and military vehicles but probably no more than two decks.

Photo of Hughes H-4 Hercules, Public Domain

@RalphJ: There you go. Answer edited. I didn't initially include it because I couldn't really find a picture that showed the similarity well and which wouldn't require obtaining copyright permission. Someone will probably suggest Boeing Clipper next and it will end with arguments about Ekranoplan etc. ;-)

That's a nice picture, and I promise I won't suggest going into the Ekranoplan!  Dang, but Hughes' plane was a beast!

This was part of an ad campaign for Timken Roller Bearings in 1946. It is a drawing by George Shepherd.

I'm disappointed that it does not exist. Thanks for the answer

It's worth noting that the (magnificent) recent Ghibli animated biopic film The Wind Rises features craft something like this in the dream sequences.  (It's a movie about Jiro Horikoshi, the dude who designed the Zero.  The film features both absolutely realistic actual aircraft, and in the dream sequences, strange fantasy aircraft.)

Nice find!

That would be an interesting hotel idea.

@jjack - Are "would it fly" questions off-topic?

@jjack: It does look like something the engineers of that time would had designed if they had ever gotten the money to do so. What would make it unflyable is only the absolute size and the inexorability of scaling laws.

@Fattie If you like The Wind Rises you might also like Porco Roso.

hey @Chloe ! right, I'm very familiar with it!  :)  Happy New Year ...

Great info here giving the year of the commercial illustration in question.  Interestingly, it seems the Boeing 314 Clipper basic info on that was retired that same year.  What a forward-looking time.

How About the Dornier Do X
Dornier Do X on Wikipedia

@mins perhaps I am missing something, but this seems like a very decent attempt at an answer.

It seems to have far less in common with the fictional aircraft in the picture in the question than aircraft shown in earlier answers.

This is the most accurate and informative answer here, in the search for the real equivalent of the illustration in question. Good one!

That thing held the record for twenty years for number of people carried in a plane.

The only successful plane with inhabited wing might have been the Junkers G.38, (which was explored in Germany by the character in studio Ghibli "the Wind Rises".)

SaRo P.192 "Queen"

Ah, that's where the engines are. I was wondering.

the  second plane looks like a space craft, a war space craft to be honest

Quite right, as I mention above ... It's worth noting that the (magnificent) recent Ghibli animated biopic film The Wind Rises features craft something like (the OP image) in the dream sequences. (It's a movie about Jiro Horikoshi, the dude who designed the Zero. The film features both absolutely realistic actual aircraft, and in the dream sequences, strange fantasy aircraft.)  The sequences involving the Junkers G.38 have perfectly realistic exteriors, and the interior is kind of a larger-then-life dream-fantasy.

That 5-decker design is outdone, amongst never-built flying boats, by Norman Bel Geddes' Airliner No. 4 design concept from 1929, with nine decks:

Ahhh .. Norman Bel Geddes.  Brilliant answer!


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Why does Boeing 737 use 2 Inertial Reference Systems (IRS) and GPS?
According to this website the Boeing 737 aircraft use 2 IRS and 2 GPS: IRS L & IRS R. Why? Apparently they are totally independent of each other.
Could somebody explain a little bit why they need 2 separate GPS and 2 separate IRS?
Follow-up question: this same website states: "POS INIT is used to enter the aircraft position into the IRS's for alignment". What is meant by "alignment"?

Related question

For the same reason they use two engines: Redundancy.

Or at least two of everything, and everyone, too.

Could somebody explain a little bit why they need 2 separate GPS and 2 separate IRS?

So that if one fails, the other can still be used to complete the flight.
Airbus even have 3.

What is meant by "alignment"?

Initialization of the system and solving the "heading problem" through a magnetometer. But this is a different question.

Thx for your answer. But if it is only for redundancy and they do not communicate amongs eacht other. How do they compensate the differences in measurements of both systems? 3 isn't that overkill?

@traducerad there is usually a third system that performs what is called "voting and monitoring"

"a third system", what system compensates the difference in measurements of both systems?

@traducerad as I said, the "voting and monitoring" one? IIRC, with two INSs, the pilots perform this function, as one uses INS R and the other uses INS L.

@traducerad, The use of 3 identical systems is what is known as triple redundancy. Let's say you have only have 2 systems, and 1 of them begins to show different readings than the other. How do you know which to believe? With 3 systems in total, if 1 begins to show different numbers, you will know that the 2 other ones are more than likely the "correct" ones.

@traducerad - redundancy is what keeps the plane safe should something go wrong with a single system. I'm sure that manufacturers & airlines would love to do away with redundancy because it adds weight, complexity and cost which take away from cargo capacity, range and profit. However, they prefer to not have the bad publicity of planes falling out of the sky due to a failure in a single system. There are probably many single-system failures every day that have essentially zero impact on a flight arriving safely due to the redundant systems.

Actually, the "heading problem" is solved by waiting long enough to sense the rotation of Earth. Magnetometer is not particularly useful due to the varying declination.

@JanHudec you mean that at (or very close to) the Equator it is not possible to solve it? (Earth's rotation cannot be sensed there). Could be a mix of the two approaches, personally I have seen it done mostly with magnetometers, so I can ascribe to unfamiliarity the reason why I haven't thought of what you mention.

@Federico, no, it is easiest to solve at Equator, because there the axis of rotation lies in the local horizontal plane. The methods are actually both used, because magnetometer gives magnetic heading, and that is used for heading indicator, while the gyroscopic method (gyrocompass is a gyro with attached weight so the axis is horizontal, but I expect IRS to simply spin up all axis gyros, measure the rotation and align the coordinate system accordingly) gives true heading, which is needed by the inertial navigation system.

@JanHudec oh, you're right. I don't know what I was thinking yesterday evening :|

Could somebody explain a little bit why they need 2 separate GPS and 2 separate IRS?

Because airliners falling out of the sky or disappearing without a trace is not acceptable from either a political or financial standpoint. Stuff fails and so backups are needed to keep the flight on-track when it does.
Having two systems of each type makes it easier to automatically detect failures, having two different types of system helps avoid systematic issues that might affect two systems of the same type equally.

Follow-up question: this same website states: "POS INIT is used to enter the aircraft position into the IRS's for alignment". What is meant by "alignment"?

Inertial navigation relies on a double integral. The sensors measure acceleration, the acceleration must be integrated numerically to get velocity, and velocity must be integrated numerically to get position. Gravity and rotation complicate the picture even more.
The trouble with integrals and particularly double integrals is they tend to compound errors over time. A constant error in acceleration translates to a linearly growing error in velocity, which translates to a quadratically growing error in position.
So, to maintain acceptable accuracy, intertieral naviation systems must be frequently re-set to the aircraft's real position while the aircraft is staionary on the ground.

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What is this plane seen in Mobile, Alabama?
This was taken at the USS Alabama in Mobile, Alabama. It is probably a US Navy aircraft.

It's a B-52, not sure what variant.

Was type aircraft NOT on the information plaque you can see on the left side of the photo?!

@Michael Hall-He may not have been at the museum but looking at a picture taken there.

That is a USAF B-52D. These were used extensively in Vietnam, and were retired after. The 2 models that remained in operation after 1983, when the last D-model was retired, were the G and H models. The G models were retired in 1991, leaving only H models still in active service. They are expected to last into the 2050s. The last B-52 built was in 1962, which means that the aircraft will have nearly a century of service. I am honored that I was assigned as a B-52G Crew Chief, 1989-1995

It is a B-52 called "Calamity Jane". Not a navy aircraft because there is no way they could fit that behemoth of a plane on an aircraft carrier.

Welcome to [aviation.se]! Does this post really add any value beyond the accepted answer?

Not all Naval aircraft are carrier based.

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Why would a Mode-C transponder report a different altitude than an altimeter/GPS?
This is related to a small single-engined plane.
On a recent flight, the controller kept telling me that I was 300 ft higher than it appeared on my altimeter and GPS (which were in sync). This was not a problem on the previous two legs of the flight. However, multiple controllers thought that my altitude was 300 ft higher.
Has someone run into this issue? What could be the problem?

It sounds like there was an issue with your altitude encoder

The transponder depends on an external altitude encoder to provide the
  digitized pressure altitude that the transponder needs for its Mode C
  replies. The encoder is connected the same static air line as the
  altimeter and is wired electrically to the transponder.
AR-850 The encoder may be either a separate unit ("blind encoder") or
  integrated into the aircraft altimeter ("encoding altimeter").
  Encoding altimeters save space and help ensure that the encoder and
  altimeter agree, but they are fairly expensive.

If you have a blind encoder its possible it can report erroneous information with out affecting other instruments onboard. You should alert your mechanic (or the mechanic that takes are of the aircraft in question) to have this checked.

The encoder/transponder has to be checked with test equipment, and a leak test of the static system done, every two years by an avionics AMO if you want to fly in transponder airspace in Canada.  An encoder could easily drift in that time.

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Is it true the F-16 has never lost a dogfight?

(Source)
I have heard the F-16 has never lost an air-to-air dogfight - is this true?

It’s the pilot not the plane. :)

My friend's little Cessna 150 has never lost a dogfight either, at least since he's been flying it.

The guy talking about the only air-to-air loss being caused by a collision is wrong. That doesn't even count as an air-to-air loss.
The real air-to-air loss was in 1996 when a HAF Mirage 2000EGM shot down a TuAF F-16D with a Magic-2.
Link(wiki but accurate): https://en.m.wikipedia.org/wiki/1996_Turkish_F-16_shootdown

No indication that a dogfight happened, and seems the Greek government denies the entire event happened.

Both countries denied the shoot down at the time, because earlier that year they came to the brink of war during Imia Crisis and the killing of two Greek-cypriots in the Buffer zone of Cyprus . News about a shoot down would spark an outcry for war during 1996, so it was agreed by both countries to keep the shoot down a secret. A lot of retired personnel from both sides confirmed it unofficially (Turkey has confirmed it officially since 2012), and greeks even painted a kill mark on the m2000 before they were ordered to remove it. https://pbs.twimg.com/media/EgWBoGHXYAANTT3?format=jpg&name=small

There are presented several results for F-16 vs MiG-29 during close-range dogfight training. One experiment was done in Germany between Luftwaffe MiG-29 and NATO F-16. There are some claims that in close-range dogfight training MiG-29 had 49:1 wins against F-16, however the real combat experience shows that MiG-29 has many loses (F-16 has a 92:13 kill/loss ratio, with MiG 29 having a 16:28 kill/loss ratio). Moreover, the study states that in current circumstances the chance of close-range dogfight is about 5%. More on close-range air combat is discussed here.


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Do today's aircraft still have INS (inertial navigation system)?
Do today's new aircraft like Boeing 787 still have INS (inertial navigation system)?

Short answer
Aircraft still use inertial navigation systems because INS is autonomous, it doesn't need any external support to work, it provides more information, and is more accurate than a GNSS in the short term. There is no plan to stop using it.
On the contrary, INS is required for certain operations. For instance the B787 cannot be flown without at least one IRU operative. See B787 Master Minimum Equipment List MMEL, item 21-01-01 page 182.
The usual solution for air navigation is to use INS, frequently updated by GNSS to contain drift, as long as GNSS signal is available, accurate and reliable (professional GNSS receivers are able to determine their reliability).

GPS/INS sensors fusion, source

Details
While INS has several disadvantages, namely initial alignment time and drift, it has also unique capabilities:

INS is autonomous, position is determined without external cooperative support.

INS position can be updated 1,000 times per second.

INS provides position information like GNSS, but also orientation (attitude), rotation rate and related accelerations. In the short term these data are very accurate. For example, the yaw damper uses instantaneous motion data to counter Dutch roll.

INS provides True North direction.

On the other hand, global navigation satellite systems (GNSS):

Contrary to inertial navigation systems (INS), are dependent on a lot of factors to work, including space vehicles, ground stations, antennas, or solar activity.

GNSS signals can be obstructed, altered or jammed.

GNSS is updated at a slow rate (e.g. once or 10 times per second, that is by increment larger than 20m for an airliner at Mach .85), due to the heavy computation required to extract and process the weak GNSS radio signal.

The best known GNSS, the American Navstar GPS, is a military system funded and managed by US Air Force.

While GPS is in effect always accurate for civil uses, it must be remembered there is no guarantee from the US DoD on that. The Navstar GPS operational specifications for SPS (civil) service allows for 72 minutes per day (2σ / 95th percentile) with a DOP > 3, that is more than 17m horizontally and 37m vertically. During these 72 minutes, the error is unlimited.

In the field of aviation, GNSS and INS are more and more coupled with air data and magnetometers, that's called data/sensor fusion to take the best of each system, cross check results and detect sensor failure.
As a everyday life example: Without an inertial sensor in a car "GPS receiver" (more accurately: a GPS-aided navigation system), the navigation system would be helpless at roundabouts. The GPS receiver instantaneous precision, its low update frequency, and its lack of orientation sensing would prevent it to correctly derives the actual position and the closest roundabout exit.

Do aircraft really use 1Hz GNSS? Receivers with 5Hz and 10Hz capability have been widely available for some time now.

@hobbs: You're right. That's still a large "blind distance" between fixes. 1 Hz is 280 m at 1,000 km/h, 10 Hz is 28 m.

To answer the specific question on the 787, yes.
According to this article

Boeing 787 avionics overview
Rockwell Collins provides the flight deck display system, pilot
  controls....Earth reference system (inertial navigation)....

In the more general sense pretty much all the big stuff flying (as far as I know) still has an INS unit. This may be due to the aircrafts age in that it simply comes from a time this was cutting edge. In the newer case they are still used to cross check GPS accuracy you can find more on in this answer (and dangerously close dupe).

Absolutely.  Both intercontinental civil aircraft and military aircraft are equipped with GNSS updated solid state INS systems using ring laser gyros for positional detection and navigation.

Can confirm that the T-38, F-16, and F-15 utilize RLG INS systems - sounds like they work pretty well, especially when linked to GPS positional updates

Modern aircraft have an “inertial reference system”, which has the set of gyroscopes and accelerometers and is used to feed all systems that need those data.
The attitude, its rate of change, and accelerations (vertical acceleration is wing loading, lateral acceleration approximates side-slip) are used for:

Attitude indicator, obviously.
Also heading indicator.
Pitch and roll flight envelope protection on aircraft that have it (Aribus from A320 on, Boeing from 777 on and some other).
Autopilot and yaw damper. Altitude and heading respond too slowly to changes in control input, so those modes also need attitude and accelerations as intermediate references.
Flight laws. On Airbus even the manual control selects wing loading and roll rate and the actual control surface deflection is calculated by the computer, so it needs the wing loading (vertical acceleration) and attitude values.

The position is integrated. This means it accumulates error over time. However, there is never large error over short time. It can be also updated at high rate, usually 100 to 1000 times a second.
On the other hand, GNSS (e.g. GPS) does not accumulate error, as it does not rely on the previous measurement when doing the next, but it has slower update rate, usually only 1 per second, and it oscillates around the actual position with variable error magnitude of which can only be estimated to limited degree.
Therefore combining the two systems give some advantages:

INS interpolates the position, providing higher rate of updates to the autopilot, so it can follow defined route more precisely.
Since each system has different kind of error, cross-referencing them provides higher accuracy then either system alone.
INS provides fall-back in case GNSS (which may fail or lose precision for external reasons) fails. This is especially important when flying Required Navigation Performance (RNP) procedures. These are in places with limited terrain clearance like narrow valleys. If GNSS fails, the INS allows enough time to safely climb out of the terrain (and divert) before it accumulates too much error.


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Does the altitude or attitude of an aircraft affect GPS accuracy?
Of course we are assuming an effective signal is being received.
I live near Idaho Falls, Idaho with a field elev of 5300ft. If I shoot an approach will GPS be more or less accurate then landing at Seattle or LA?
Does the accuracy of GPS change with aircraft altitude or attitude?

Altitude has little effect, as long as you don't descent into a valley. Mountains shield the GPS signal, resulting generally in lower accuracy and lower integrity levels.
Attitude does matter, steep turns can result in the airframe shielding GPS signals from the antenna. Again, the effect is a lower accuracy and integrity.

The issue is what kind of accuracy you are referring to.
If lateral accuracy, the best geometry is to have satellites distant and just above the horizon.  In general, this offers the best solutions for lateral positioning.
If altitude accuracy, it is helpful to have satellites more above you, or at least not near the horizon.
Attitude of the aircraft will impact the reception from one or more satellites, and can cause a change in signal reception which will have the GPS seeking different satellites for it's solution, which might result in short term changes in accuracy.
Furthermore, high altitudes provide more satellites with stronger signals, less terrain masking of distant satellites, and less error inducing signals like multi-path.  Lower altitudes tend to have not only more multi-path and similar interference but also terrain interference, where flying near or below terrain will interfere with reception, particularly of distant near horizon satellites.  In that case there may be more positional "errors" or less accuracy.
With normal aircraft installations, unshielded by terrain, and with normal constellation visibility, there is little practical difference in normal flight operations.
This answer is a general, aviation oriented answer. There are literally hundreds of peer reviewed papers on this topic, rich with substantiation of various phenomena, models and theories.
Addendum. To address your specific question regarding approach accuracy at higher elevations, it is important to factor in terrain. If one was flying an approach in a valley, there may be some terrain masking of GPS signals. This would be a factor of the relative terrain.  However practically speaking, there is no difference.  Because the GPS unit will assure that it has adequate signals from adequate satellite transmitters, to assure the precision needed for the approach.


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What is the meaning of the crosshatch marking on altimeters?
What does the crosshatched area on an altimeter tell you?  It's only visible when below 10,000 ft indicated altitude.  Can't be terrain awareness, a lot of terrain around here is over 10,000 feet.
This sample altimeter display from the FAA manual on flight instruments shows the crosshatched area:

Here's the accompanying text from the manual where it points out the crosshatched area:

Crosshatch flag: A crosshatched area appears on some altimeters when displaying an altitude below 10,000 feet MSL.

It looks like the crosshatch (or barber pole) indicator doesn't have a consistent meaning (a similar marking is used on some airspeed indicators, by the way). I found several different examples of when it can appear:

Below 10,000' (FAA PHAK; Army RC-12H manual)
Below 15,000' (instrument service catalogue)
Below 16,000' (another instrument catalogue)
Above 0', i.e. above sea level (instrument repair information)

The only source that gave any explanation is the last one:

When the altitude is below sea level the barber pole is no longer
  visible. This is provided to avoid the error of reading –1,000 Ft. as
  being +10,000 Ft.

After following a bunch of links and skimming some discussion forums, my conclusion is that @RalphJ is probably right: manufacturers added the flag to highlight that the aircraft is at a relatively low altitude, in a way that's much easier and quicker for the pilot than 'parsing' multiple hands on the altimeter face. And the fact that different sources give different altitudes highlights an important point: it's always a good idea to read the handbook or manual for all your instruments because you can't assume that everything works the same way in every aircraft, even something as 'simple' as an altimeter.

+1 for this statement it's always a good idea to read the handbook or manual for all your instruments

It replaces to 10 thousands digit, evidently because X9000 has been found to be easier to read than 09000 or just blank space before the 9000. That crosshatched area would also scroll to display "NEG" if the altimeter is displaying an altitude below zero feet (i.e. Below sea level or below the reference datum plane).

If you find any research that supports the claim, please add a reference.  I agree that is the most likely explanation, but I have yet to find any supportive research.

Also note that for lower altitudes, 1000 could be easily confused with 10000, so the prepended 'X' creates a more obvious difference in appearance (as opposed to a blank).

@RockPaperLizard -- this requirement was written in blood, not research papers -- there have been several CFITs where the misreading of a three-pointer altimeter has been a contributing factor.

I just reread the question and this answer, and I'm wondering if this answer is talking about a related, but different, altimeter design element.  In the OP's image, the crosshatch is a discrete area, whereas in the answer, the crosshatch is referring to an 'X' that replaces the digit zero.

Agreed @RockPaperLizard, I read the Q and A a few times and can't figure out how this relates to the question exactly.

@zymhan As best I recall, this answer came before the edit that added a photo to the question. On an electric altimeter with a single hand & scrolling digits, this answer is descriptive; for the present state of the question, it isn't responsive any longer.

If those marks are visible when you are lower than 10,000 ft above sea level, and if you can't see the barber pole, you are flying higher than 95% of ground surface level on Earth. See hypsometric chart. So, visible altimeter barber pole tells you should still worry about altitude... (of course, this model of altimeter assumes "sea level" by the barometric pressure you set on it).

https://tghaviation.com/aircraft-instrument-services/getting-to-know-your-kollsman-window-and-barber-pole/ -- says barber pole shows whenever above sea level

Crosshatch also in some of pressurized aircafts predicts the caution to pressurize or de-pressurized while ascend or descend respectively. The indicator in some aircraft automatically pressurize the aircraft using electrical signals as precautionary to pilot and passenger safety to get into a partial or total hypoxia.

Welcome to the StackExchange. Do you have a source for your answer? The reason I ask is that:

10000 feet is a rather arbitrary number for pressurization purposes; 2. Pressurization is controlled by a separate device and guage that measures cabin pressure altitude instead of MSL; 3. Pressurization equipment is usually set to 8000 feet; 4. 10000 feet represents the altitude at which speed restrictions apply in the US NAS.

This makes no sense; what value is there in a crosshatched warning flag that goes out of view above 10k when the need to pressurize is greatest???  Beyond that, in my experience this explanation is simply incorrect. Pressurization manually initiated at 10k? Never heard of such a setup.

Also, this alert flag would not at all assist the pilot in case of a slow depressurization or equipment failure.

You may be confusing this with the cabin pressure altitude gauge which measures the inside air pressure of the airplane in its equivalent feet of altitude at ISA. It would look similar. The crosshatched alert would work in the opposite manner as the one the original poster asked about. It would also not be located on the instrument panel in the same location as the six pack. It would either be with the engine gauges or a separate panel along with the pressurization controls. Since it works automatically, there would be no need to monitor it as closely as flight instruments.

May be silly, but why not a reminder we're at 4000 feet rather than 14000?


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Object on the flaps?
I was on a intercontinental flight to the US and noticed this object shaking with the wind and moving as the flaps change position. Is this normal? I have never seen this before. Is it safe to travel with this kind of item on the trailing edge?

Looks like a rubber gasket came off the track fairing, nothing too critical. I'm pretty sure we've had this question before, but your phrasing makes this one stand out :) (edited out in less than 5 min)

Is that an inter-flap seal that has become dislodged? It that's the case, it's not unsafe, but maintenance would need to straighten it up.

Thank you for your answers. Then.. is it ok to take off with that problem? Or the plane shouldn’t have departured till it was fixed? I noticed the cable going out before departure

What was the aircraft type? I cannot tell from the pictures (though I'm sure some of our regulars can) and it would help get an accurate answer. You can usually find it on your ticket.

It is a Boeing -767-300


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Does preheating fuel before it reaches the turbine result in a performance improvement?
Preheating fuel before it reaches the combustion stage was first proposed several decades ago as a way to improve mixture, fuel economy, and to reduce emissions in car engines.
One example of this method being used in aviation was the Polish jet trainer PZL TS-11 Iskra. Overlooking mechanical complications which may be introduced by using fuel preheating (including vapour lock), does this method have any measurable benefits in aviation in terms of performance or fuel efficiency?

I'm confused as to what you are asking, you say you ignore results?

Fuel heating systems are used in some aircraft to prevent the fuel from gelling, not sure if that's what you are referring to. If not, please post some details on the system to which you refer.

@Urquiola I've edited your question so that what's being asked is clearer to readers. Please have a look when you get the chance and review the edit for correctness.

The key here is understanding the purpose of pre-heating. Combustion occurs very rapidly to produce the power stroke in piston engines and thrust in jets.
It's time in the combustion chamber to do so is measured in fractions of a second.
Ideally, a mixture of 2 gasses, methane and air for example, would ensure efficient and complete combustion.  This is your common kitchen stove.
Mixing liquids with air is more problematic, as now you have a mist of small droplets instead of ready to mix gas.  This is good and bad.  The good is the evaporation of the fuel helps keep the engine cooler. This is a benefit of "full rich" setting.  The bad is the fuel is not mixed as well with the air when it burns, lowering efficiency and releasing harmful byproducts such as carbon monoxide.
Proper design (operating temperature) and choice of fuel may eliminate the need for pre-heating, especially once the engine is "warmed up".
Aside from the dangers of heating fuel, gains may be made by standardizing the temperature of fuel inflow for pollution control. Another possibility is to use the heat from turbo compressed air to warm it.  Tight control of octane rating is also beneficial.
But aircraft operators adjust their richness based on RPM and usually on the rich side to avoid overheating the engine, which is far more disastrous than slightly lower fuel milage.
In design, using engine heat to evaporate the fuel may eliminate the need for pre-heating, except for extreme arctic applications.


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Best glide speed vs. best glide angle? Maximum glide range?
I have some open questions regarding best glide in a descent:

I understood, that there is a best glide speed. This best
glide airspeed occurs at the highest lift-to-drag ratio (L/D). This best glide speed is normally given in the operator's manual of the aircraft.

Is it true, that this best glide speed is given in terms of indicated airspeed IAS and hence is independent of the elevation?

What about the sink rate when flying at best glide speed? I have seen hodographs where the sink rate is given over airspeed. (Diagram taken fom Taken from: Coombes, Reachability analysis of landing sites for forced landing of a UAS)

Is this again inidcated airspeed IAS?

As we all know, the TAS decreases with decreasing elevation when maintaining a constant IAS. For navigation with respect to earth's surface I need ground speed GS which is directly related to TAS via the wind speed (which we can assume to be zero for the moment)
To determine the glide path angle I suppose, that the ground speed and the sink rate is relevant.

Supposing, the best glide speed is IAS contrary to true airspeed TAS, how can I determine the glide range?
What is the resulting flight path angle when maintaining best glide speed? Does it change with decreasing elevation?

My intuition tells me, that when flying at constant IAS, the flight path angle should get steeper with decreasing elevation.

Is this assumption true?
Every reference to clarify these questions is welcome.
Currently I try to implement an autopilot for an emergency landing assistant that maintains a constant flight path angle during gliding descent. This enables me to exactly determine the distance traveled when I know the starting and the end elevation which in turn allows to do a proper path planning. My gut feeling tells me, that in this case I don't make use of the maximum possible gliding range as I have to start with a too steep flight path angle at high elevation to maintain this constant till the ground.
Is there any good idea how to predict the distance traveled when only knowing the start and target elevation?
Thanks a lot and Cheers,
Felix

See also How does wind affect the airspeed that I should fly for maximum range in an airplane?

"As we all know, the TAS decreases with elevation when maintaining a constant IAS" - really? I didn't know, and am still in doubt.

@PeterKämpf is correct: True airspeed increases with altitude for constant indicated airspeed.  Also it is better to define 'best glide'.  You are referring to best L/D speed, which is the flattest glideslope.  The other 'best' speed is minimum sink speed, which is slower.  Min sink speed will keep you in the air for longer, but will not get you as far through the air as best L/D speed.

@a.out: You are both perfectly right and I formulated it in a mistakable way: it must be: "As we all know, the TAS decreases with decreasing elevation when maintaining a constant IAS."

Is it true, that this best glide speed is given in terms of indicated airspeed IAS and hence is independent of the elevation?

Yes. The best glide speed needs you to fly at the optimum polar point, and with the same IAS you will fly at the same lift coefficient and polar point.

To determine the glide path angle I suppose, that the ground speed and the sink rate is relevant.

No, the angle will be the same regardless of altitude (if we neglect Reynolds number effects for now). What does change is the speed over ground - this goes up with height.

What is the resulting flight path angle when maintaining best glide speed? Does it change with decreasing elevation?

No, it doesn't. The glide path will be the same, only at higher altitude the airplane will fly faster and proportionally sink faster. What changes is the time scale, not the geometric scale.
EDIT:
The added graph is either given in TAS on the x scale and for a specific altitude, or it is given in IAS and valid for sea level to maximum ceiling (if we neglect Reynolds number effects for the moment). Note that at higher altitude the airplane will fly faster and proportionally sink faster, so the indicated sink speed in the second case must be multiplied with the square root of the density ratios between ground and actual altitude to arrive at the true sink speed.
P.S.: Terminology:
Altitude is the vertical distance from sea level to where an airplane flies. See here for more.
Elevation is the vertical distance from sea level to the ground or to an obstacle.
Height is vertical distance between an aircraft and the local ground.

Well, there's a tricky point here in that if x axis is given in IAS not TAS, then the vertical scale also needs to be thought of as "indicated" not "true".  I.e., if you change the altitude for which the graph is intended to be valid, you would have to make a change to the vertical speed scale, if it is meant to be in actual real units of meters per second.

@quietflyer Right, I do mention that at higher altitude the airplane will fly faster and proportionally sink faster, and assume that people keep that in mind over two sentences. Maybe that is too optimistic.


text:
Scalloping vs Site error in VOR
I am not able to understand the difference between scalloping and site error in VOR because the theoretical defination of both of them is almost same

Quote the definitions you’re confused about?

See at the end of this answer for the difference between scalloping and bending errors, and the definitions in ICAO documents (near this picture).

Scalloping error is smooth variation in the path  provided by the VOR(radial in case of vor) within the specified limits.
Site error is the error in VOR signal due to site problem like terrain, alignment error, equipment error etc.

Can you please elaborate regarding scalloping. What does smooth variation in signal means


text:
What was the flight route from New York to Paris that Air France took in 1955?
I have a photograph of me and my sister in 1955 or 1956 boarding Air France to Paris. I seem to remember the route was:

New York - Gander
Gander - Shannon
Shannon - Orly

Is that correct? I know the return flight (westbound) was that route. Does anybody know how long it took?

Welcome to Stackoverflow Aviation, could you please reformulate your question and explain what you would be looking for.
I suppose there are several flights, even for 1955 1956, that would cover these destinations, so it would be useful to have some more details too regarding what you are seeking.

Hello Merrily. Welcome to Aviation Stackoverflow. I've edited your question in to make it a bit clearer for our readers. I hope I didn't misinterpret your intentions. Feel free to edit again.

It would be helpful to know the type of aircraft used, which could be identified from the picture. I’m not asking you to upload your doubtlessly personal picture, but are there any details of the aircraft you could share?

@CptReynolds:  According to this 1955 Air France timetable, they were using Lockheed Constellations & L-1049 Superconstellations for their New York–Paris service at the time.  (Unfortunately, the timetable doesn't mention refueling stops as far as I can tell.)

...  and as of 1957 they were advertising their brand-new non-stop New York–Paris service on their L-1649 Starliners.

This is a fantastic question.

The route was IdleWild (renamed JFK in 1963) or LaGuardia -> Gander, Canada -> Shannon, Ireland -> Paris. The trip took a total of about 18 hours going eastbound with tailwinds, and 24 hours going westbound with headwinds.
Gander was opened in 1938 and continues to be the preferred refuelling stop for aircraft that can't make the hop across the north Atlantic in one go, simply because it is the northeasternmost point on the North American continent where such a facility could be built. For a while it was the largest airport in the world, and was used extensively by the military during WW2 as a stopover point for aircraft being ferried to Europe.
Air France used the route from the beginning of their transatlantic service in 1946 until the late 1950's, when the jet age made it possible to fly the route non-stop.

Sometimes they used the southern route.
ORL to Azores to Gander to IDL.
Or ORL to Azores to Bermuda to IDL.
Sometimes instead of Gsnder they stopped at Goose Bay.
AND even with jets, they still had to stop for refueling on westbound flights. They often still do on certain aircraft flying the route.

3 downvotes and no comments on why? I don't see why this answer is so bad. Though I disagree that "they often still do" stop halfway across the Atlantic, as I'm not aware of any major scheduled flights that stop to refuel in Canada.

That's because you are not a pilot and you do not ferry aircraft across the Atlantic. Nobody said that airliners still use Gander for refuelling, only aircraft that can't make the hop in one go. Also, Gander is often the airport where airliners return to North American soil after being forced to turn around on the way over.

I was not the one downvoting …. until now … but the second suggested route does not really make sense. It is both longer and has longer longest leg, so no advantage there. Plus no reference.


text:
How do CH-47 pilots lower the tail during a pinnacle landing?

(thedrive.com)
Given the recent rescue of a climber on Mt. Hood by a Chinook, how are the pilots able to lower the tail in this situation? Is this just the natural angle during a hover, or are there some adjustments the pilots can make to the fore and aft collective individually?

Related: Why would a helicopter hold a 'nose-up' in hover?

Related

I wonder what would the angle inside looks like.

A careful balance of nose-up cyclic and decreased collective to stick the aft of the ship firmly in place. Not so much a landing, as flying with the aft gear and ramp planted.

Because the helo is barely hovering in level flight with the aft landing gear resting on the inclined snow pack.  It doesn’t lower its tail as such.


text:
Could hydrazine be used as a scramjet propellant?
Hydrazine is used a monopropellant in Satellite OMS rockets. But interestingly enough, it's highly exothermic decomposition into ammonia, nitrogen, and hydrogen provides heat for an endothermic reaction with additional hydrazine to form hydrogen gas. So a scramjet using hydrazine would have to reactions inside it's combustion chamber: The decomposition of hydrazine and the combustion of the resulting hydrogen gas with air. And unlike hydrogen gas, hydrazine has much higher propellant density. Has this ever been considered by aerospace engineers and even tested?

General Electric has a patent on it, granted 28 years ago.

Does it offer more energy density than conventional fuel? If no then why?

Technically yes, you could use hydrazine in a scramjet.
But there's no reason to do so. The singular purpose of building a scramjet is to get air into the combustion chamber, so that you don't have to use a monopropellant, which all have high cost and poor energy density.
Kerosene or H2 won't burn without air, so you need a scramjet or an oxygen tank to burn them. Hydrazine doesn't, so you can burn it in a rocket, at higher pressure with more efficiency and better aerodynamics.
Advantage: Rocket engines have a thrust:weight ratio of up to 133:1, scramjets about 2:1. So an equivalent rocket is up to 66 times lighter than a scramjet.
GE's patent refers to the use of a small amount of hydrazine in a catalyst-like role, or more accurately to act as a fuel/air mixer.

What I was actually describing is hybrid engine of sorts: Part rocket engine, part scramjet. Initially the hydrazine would act as a monopropellant from startup to get the vehicle up to a sufficiently high speed. Once it reaches ~mach 5 it would work as a hybrid engine. The idea is that it would produce a lot more thrust than a typical scramjet and have a higher thrust-to-weight ratio. Making it much more efficient and giving it longer range.

Once you reach such high speeds using a monopropellant would likely be thermally inefficient due to the mass flow of air through the combustion chamber in addition to much lower chamber pressure.

The Scramjet is an AIRbreathing engine.
Thus there's no reason to incorporate hypergolic fuels because that requires it's own oxidizer onboard weight.
Second, with an energy density of 19.5 Megajoules per kilogram; it's half energy density of diesel fuel. Basic jet fuel has a energy density 43MJ/kg both of which make a better fuel with NONE risky toxicity issues

In addition to it's use as a monopropellant, hydrazine has been used as a fuel in bipropellant combinations, for example in a 30% by weight mix with 57% methanol and 13% water, with concentrated hydrogen peroxide as the oxidiser in the Messerschmitt Me163 rocket propelled interceptor. This suggests that it's use as a fuel in a scramjet engine might be technically possible, although it is chemically unstable and toxic in pure form.


text:
Could hydrazine be the jet fuel of the future?
It is true that hydrazine is highly toxic and explosive, but it has tremendous energy density. The decomposition of hyrazine into hydrogen and nitrogen gases AFAIK produces enough heat to ignite the resultant hydrogen when it occurs in the presence of air. But to make it useful for low speed, subsonic jet propulsion would involve tightly controlling the decomposition and combustion processes. Is this possible? And has there been any attempt to design jet engines that use it?

Liquid Hydrogen would be preferable in terms of energy density (eg. 6 times more energy density) but is terrible to store for prolonged periods without maintenance, thus hydrazine or comparable fuel is used for maneuvering rockets.

Hydrazine is only advantageous as a rocket fuel in that it does not require an oxidizer to be stored on the rocket as it is a monopropellant.  Not having to store an oxidizer on the rocket can save some weight but even then rocket designers prefer other fuels due to their higher energy densities.

Cost per gallon, toxicity end that dream.  But it does inspire looking into putting catalytic elements into a hydrocarbon turbine to reduce NOx emissions.

@Adwaenyth but it’s terrible for energy density by volume which is at a premium too in an aircraft. Also risk of explosion.

A quick look into wikipedia (https://en.wikipedia.org/wiki/Energy_density) shows hydrazine (in full combustion to N2 and H2O) at 19,5 MJ/kg while Jet-fuel is listed at 43 MJ/kg.
So => no

Indeed, pretty much anything that is or was at some point used as fuel has a higher energy-density than Hydrazine: Methanol, Ethanol, Diesel, Gasoline, even coal! In fact, Hydrazine is only slightly better than cow dung. Not sure why that would be considered "tremendous".

The high energy density of coal isn’t really a surprise, it’s just that having a crew to shovel it into a rocket nozzle is difficult to organise, especially in an expendable first stage.

Hydrazine is sometimes used to power an APU (e.g. for the F-16). APUs are generally turbine engines, so hydrazine turbines exist.
For rockets, there's a movement away from hydrazine and other nasty propellants toward less toxic alternatives. There's little chance aviation will move in the opposite direction.

It has roughly 50% lower energy density than jet fuel, so obviously worse, but still much better than any rechargeable batteries. If we could use it directly in fuel cells, which generally have efficiencies approaching 60%, which is twice as good as piston and turbine engines, then we could actually get a system performance similar to that of jet fuel.
A big problem with hydrazine is toxicity. It is comparable to ammonia, but somewhat mitigated by the fact that hydrazine has a much higher boiling temperature, comparable to water. Hydrazine fuel system would need to be engineered to avoid an vapor emissions. Another problem is the fact that hydrazine can decompose exothermically in presence of catalysts, so material compatibility becomes a big issue.
This is theory. It seems doable from the technical standpoint. The question marks are economy and safety. If we were to stop using fossil, bio and synthetic hydrocarbon fuels today hydrazine is a much better option than batteries and than ammonia.

Exothermic decomposition in presence of a catalyst was the deciding factor for all practical cases where hydrazine was used in the past. I wouldn't call this a problem. Without this characteristic, nobody in their right mind would accept all the downsides of hydrazine.


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Why is there no reconnaissance version of the B-2 stealth bomber?
So the B-2 is perhaps the stealthiest plane ever made. It has proven itself in combat missions when flying by night. But given the retirement of the SR-71 around 1990, I'm surprised the USAF did not place any orders for a reconnaissance version of the B-2. Despite being much slower than the Blackbird, it is much stealthier. Obviously it would be only suitable for night missions but with the advent of thermographic(IR) cameras, it could still be very useful for spy missions over places like North Korea.

Related: Why was the U-2 so different from the SR-71? In particular from that answer: "The main reason for the retirement of spy aircraft was the advent of reconnaissance satellites"

@Bianfable one of the limitations of reconnaissance satellites is cloud cover and other atmospheric conditions. That would be the reason to use stealthy reconnaissance planes. Second of all, the U-2 and B-2 are incomparable. The U-2 is over 60 years old and is extremely vulnerable to SAMs.

Why are you so sure they have not used a B-2 for specialized missions?  Do you have clearance?

The B-2 isn't as stealthy as you may think. Networks of advanced radars combined with computer algorithms can detect it. The SR-71 could outrun missiles, the U2 could fly extremely high and peer into enemy territory, the B-2 doesn't have any desirable characteristics in a recon airplane.

Both U-2 and SR-71 were developed to counter surface-air missiles.  U-2 flew too high to intercept by the missiles anyone had bothered to build up to that point; defeated by building bigger missiles. The retort was the SR-71 and MiG-25/31, too fast to be decently intercepted by missiles capable of flying that high.  So bigger missiles still e.g. S-300, Patriot, Phoenix, R-33 etc.

Planes are ordered for mission requirement, not just for being better. It appears that no mission required a spy plane the size of the B-2.

Most of the uses the SR-71 had been developed for are now covered by satellites. Optical sensors spy on new structures and objects, infrared sensors find fires, rocket launches and explosions and radar sensors detect moving objects and can peer through clouds. The combination of data from all three sources allows deep insights about technical characteristics and capabilities of foreign developments.
A disadvantage of satellites is their highly predictable overflight schedule, so airborne assets are used to double-check and make surprise visits. However, risking a manned platform for this would open a path to escalation that is better avoided. For that reason, stealthy unmanned reconnaissance platforms have been developed which complement the work of satellites.
One such UAV, the RQ-170 Sentinel, was hijacked electronically by Iran a few years ago, so we know a little more about it. Later, Iran presented a design which was based on the US design.

Shahed 171 drone. This picture was taken at the Eqtedar 40 defence exhibition in Tehran. Attribution unknown. Source: Wikipedia.

Sounds like the RQ-170 isn't such a good design. Especially if it can be detected and electronically hijacked!

@Mr X - Nothing is "undetectable".  Even a B-2.

The B-2 was never designed to be used as a recon platform.
It's too expensive to operate it as such.
The risk is not worth the benefit given other far less costly options are available.

The SR-71 can carry about 3500 lbs of payload. The SR-71 is the right size for a mach 3 recon aircraft because if it was any smaller it would have less payload, and recon equipment weighs about 3500 lbs.
The B-2 can carry about 50,000 lbs of payload. The B-2 is not the right size for a stealth recon aircraft, because recon equipment does not weigh 50,000 lbs.

The B-2 has a payload capacity of 20 short tons. A recon version could convert some of that space into extra fuel tanks and give it extra range. It is not the size of the aircraft, it is the size of the radar cross section. The B-2 is larger but has an even weaker radar signature than the SR-71.

Because satellites.
If there was a recon B-2, an R-2, then it would also fly very high. High above (most of) the clouds.
So, you have a vulnerable aircraft that can see as much as a satellite.
For tactical recon, you might favor the short reaction time of the spy-plane; but for strategic recon it's much more effective to invest in satellites.

A B-2 is too expensive.
A B-2 costs, very roughly, \$2 billion to build $130,000/hour to operate.  At least 99% of the time it is getting maintenance instead of flying.
A spy satellite costs less than \$10 billion to build.  It has no operating costs (space shuttle servicing is no longer available) and it flies all the time.
It is also possible to just buy someone else's images. https://www.statista.com/statistics/1293877/commercial-satellite-imagery-cost-worldwide/


text:
What are the aerodynamic characteristics of the flying saucer?
It seems that Canadian VZ-9 Avrocar was aerodynamically unstable. Particularly at high altitudes, and so the project was cancelled. IIRC there was considerable interest in flying saucers in the 1950s and this was one of the most well documented attempts to build one that could actually work.
But is the flying disc a bad design for an aircraft? Especially one that is designed for high speeds high maneuverability. If so please explain the reasons for this.

I had a professor in school who was a technician on the Avrocar. The whole thing was a goofy dead end, that existed only because someone at the USAF had a bee in his bonnet and was able to get it funded. When you think about it, what was the point of a saucer shape in the first place? Flying saucers were one of the dopier 50s fads.

@JohnK I think the idea was to make VTOL fairly easy. It wouldn't need a runway and could land in a grassy field and then take right off.

Yes but why a disc and not some streamlined shape that can be designed to have some kind of static stability in forward flight, like a lifting body. The ACar might have been able to get out of ground effect with more powerful engines, and digital computers controlling the attitude control vanes in the D ring. Anyway, you are still stuck with a massively inefficient flying machine.

Ah, the '50s... real engineers at work (with a lot of money)...


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What are the fonts used in MCDU screens?
All MCDUs (and other screens) I've seen share a very similar, if not identical, set of fonts - a monospaced, sans-serif, very clean and easily readable font, often in two vertical sizes at the same horizontal pitch. What font is that? Do different instrument/airplane makers have their own? Do airlines standardize on one across their fleets?
FAA's Advisor Circular 25-11b (https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_25-11B.pdf) makes some recommendations on fonts.
Also, http://www.b737.org.uk/fmc.htm has screen photos where the pixels are discernible, presumably from an early 737 model. There isn't a name, but there is enough unique features for it to be identified, if it has an official name.

Airbus have released their current cockpit display font: https://b612-font.com/
It assumes a higher resolution than the original MCDU screens, but may still be useful for what you need.

Thanks, @vk5tu. That's amazing

MCDUs date back to the first generation FMS that was developed in the late '70s for the B757/B767 aircraft. An equipment Characteristic for the MCDU was developed by ARINC committee and published as ARINC 739. This was replaced by ARINC 739A in the '90s to support additional new features.
The ARINC 739/739A Characteristics do not specify a particular font. The regulatory agencies (e.g., FAA) don't really care as long as it is easily readable and fault tolerant. That last bit is the concern that a dead pixel/row/column in the display causes a character to be misinterpreted.
Starting with the originals, the MCDUs were limited by the technology of the displays. They settled on a 14 line, 24 characters per line (fixed pitch) CRT display. CRT fonts were raster generated. The text layout carries over to the current MCDUs when they switched to LCD displays in the '90s.
The fonts used were limited by the CRT technology and later by the available number of pixels in the LCDs. The constraints of aircraft certification generally means that things don't change unless there's a compelling (think: money) reason to do so. So even with today's high resolution displays, the MCDUs still have a 14 line 24 character layout. With more pixels, the fonts are just higher resolution versions of the older fonts.
In recent discussions concerning displays, the manufacturers want a consistent look within the cockpit, subject to the certification rules. As you found in AC 25-11B, there's some general guidance:

5.4.3 The choice of font also affects readability. The following guidelines apply:
5.4.3.1 To facilitate readability, the font chosen should be compatible with the display technology. For example, serif fonts may
  become distorted on some low pixel resolution displays. However, on
  displays where serif fonts have been found acceptable, they have been
  found to be useful for depicting full sentences or larger text
  strings.
5.4.3.2 Sans serif fonts (for example, Futura or Helvetica) are recommended for displays viewed under extreme lighting conditions.

In my experience, Futura seems to be the most commonly preferred but others do come up. Not surprisingly, some fonts are copyrighted and are subject to licensing fees which reduces their popularity.

Thanks. With your info, I was able to locate what looks like a first-gen system with pictures at https://737b.blogspot.com/2013/06/flight-management-computer-fmc.html.

Me feeling, from Boeing's display and others, is of a monospaced format, somewhat close to OCR-B. Futura is a proportional font and suffers from readability issues in small sizes, but I get where you are coming from - it's a very clean design.

You are correct in assuming that monospaced fonts are still common. Boeing and Airbus tend to be very conservative about changes in the cockpit as airlines don't pay for anything they don't need. The high end bizjets tend to have more innovation in design as the customers are more interested in the tech.

If the MCDU is 14x24 characters, a monospaced font makes sense. It's a bit curious, as the font size changes, but the grid remains the same and the spacing between characters varies.

That's the way most computer terminal displays operated until they shifted to graphical displays in the '80s (the first IBM PC display was 25 lines by 80 characters.) While you could fit more characters on a line when using the small font, they don't to simplify the display management. The MCDU is a dumb terminal. The remote app (FMS, Datalink, etc.) just sends the character strings to the MCDU where they will stay until they are overwritten. Miscount your string length and you leave stray characters on the screen.

Text-based screens are great for simple devices - hitting the memory bus to fetch 80 symbols and attributes every 8 scan lines is much nicer to the CPU (which is effectively blocked from accessing the memory until time-critical - the electron beam waits for no one - video output finishes) than having to read, say, 640 pixels and attributes on every scan line.

My guess is that these are raster (non-scalable) fonts without any special name.
At least initially, the screen resolution wasn't (and needed not be) particularly high, and the characters were the typical 8x8 pixels or only slightly better. Such fonts are drawn by hand (by pixel) and don't have too many variations to speak about. (Although the sales people might disagree).
Later models with higher-resolution screens probably modeled the same terminal-type font to keep commonality. I still doubt MCDUs have an operating system (if any) with scalable font support.

It sure looks like something in that direction. The AC I mentioned does recommend 5x7 and 7x9 as minimum pixel sizes for text and some Rockwell Collins units I've seen definitely are in the low pixel count field, with what looks like 7x9 characters for small sizes, but newer models appear to have anti-aliasing. Garmin units look, definitely, retro in comparison.

@rbanffy, interestingly, Garmin is probably in the same boat. Even in their newest glass systems (G2000 and G3000), they kept the same screen resolution as in G1000 (1024x768), and it applies to all sizes, from 10" to 15".


text:
Can large airliners be operated without ground support?
I'm wondering if large A3x0/B7x7 airliners could be operated without ground support. Short of using the inflatable slides, I guess at least stairs would be required to load/unload passengers. Apart from that, assuming fuel and push-back is not required, would it be possible to land, switch the engines and systems off and then take-off again without electrical, A/C, etc. ground support?
Bonus question:
If possible, are there any circumstances where this is routinely/occasionally done? I know that it's definitely the case for smaller aircraft such as an ATR 72 servicing remote airports - I experienced that at e.g. Luang Prabang airport.

related: http://aviation.stackexchange.com/q/2035/609

Actually ATR 72 has much more problem with this than other aircraft, because it does not have APU and running the engine (#2) with propeller brake is very inefficient. I've read story by a pilot of one who mentioned at some airport(s) it took some time to teach the ground crews they need external power, so presumably other aircraft just used APU.

In 747-100/200 and probably the other 747 models as well you can enter and leave the airplane through the nose gear. Mechanics do it all the time. It's a one-person-at-a-time operation though and requires a reasonable degree of fitness. Thus, strictly speaking you don't need stairs.

@Terry how did you climb up to the plane?  I can't imagine a ladder simply being bolted on to the gear.

@dalearn I'd have a hard time doing it now at age 78, but when I retired at age 60, as I remember, the best way was right foot on the aft part of the axle between the 2 front tires, then step up and swing left foot to the right tire top, then straighten up with the right foot on left tire top, then step up with one foot on open nose gear door structure, then the other foot. Open hatch that is now above your heard, climb through hatch on steps in structure into elec compartment, then open hatch now above you, slide carpet you see away from opening, go up rungs into very front of main cabin.

@Terry: That’s what I call an exact description :)

In a word, yes.  The APU (auxiliary power unit) will supply air pressure and power the electrical systems needed to start the aircraft.  No ground support is required.
http://www.flyingmag.com/pilots-places/pilots-adventures-more/jumpseat-its-all-about-apu
It's routinely done all the time!  Next time you're at the airport, watch a 7xx or A3xx.  Ignoring stairs, fuel, food, toilet drains etc there is sometimes no external air or power supply attached.  The APU will be running during boarding to power the aircraft and condition the cabin.  It is then used to start engines during the pushback.  When in the cabin, you will notice the packs being switched off (the packs supply cabin air) as the air is diverted to the engine starters.
The only times I've seen this not done is when an external air conditioning cart is attached as the APU cannot cool the aircraft.

Usually on the ground you will have a GPU hooked up.  It won't be a cart but a cable hanging from the jet bridge.  You are correct however, that this is not needed as starting the APU provides all needed power for the aircraft and air for air conditioning and engine starts.

There's a good example which is the A319 LR which flies scientists down to Antartica. They utilize (very) little ground support, except for the stairs (they seem to have inbuilt ones in the front as well, although these are not used on site) and the trucks to offload the cargo. APU provides the power on the ground, and the aircraft has sufficient juice in the tanks to make the round trip without refuelling.

(source: smh.com.au)
You can read up on it here. She does weekly flights from Hobart to Wilkins aerodrome in Summer. 4 hours and 30 minutes of flying right into the uninhabited :)

Cool! Exactly the kind of unusual practice I was curious about...

How is the APU restarted if it shuts down for any reason?

@hexafraction the APU itself is started from the batteries. If you have a look online you'll find videos and pictures of aircraft undergoing certification where they are parked north of the polar circle cold and dark for days only to be started with batteries and the apu.

The venerable DC-9 was designed to service small airports out away from the hubs with a minimum of equipment.  The engines were up on the fuselage rather than under the wing so that the landing gear legs could be short, lowering the fuselage.  This result let the baggage compartment be reached without the usual portable conveyor belt.  Air stairs were built into the fuselage and were deployed horizontally, until they lowered the outboard end to the ground.
Gravel kicked up by the nosegear and then ingested by the engines became a problem so the DC-9s and the MD-80s that followed had a gravel deflector shield mounted on the nosewheel.
Now the DC-9 is not a Boeing or Airbus in the original question (ok, ok, lets agree to set aside the Boeing 717 that was the final iteration of the DC-9/MD-80 family) but the principle endures:  Large commercial airliners can be designed to function nicely without a ton of ground support. However, the vast majority of commercial airports are well equipped to handle planes, so the designers of the planes have in many cases left all that stuff off the planes to save weight, complexity, and space.  So the ground support is necessary.

It is possible with the old soviet wide-bodies; they have built-in stairs and even allow for luggage stowage by the crew during boarding. This autarky led to significantly increased weight, which meant that while these planes could land at remote destinations, they suffered from incompetitiveness in inter-airport service. And well, how often would one need a wide-body to bring 350 people into the middle of nowhere?
Many military transport aircraft, while having similar size as the aforementioned airliners, can fly tanks and/or equipment into remote areas. Fedex would never buy one, though... these machines are plain incompetitive in both acquisition and maintenance.
No plane requires a pushback vehicle in a remote destination, if said destination has a rotunda big enough for a full-turn, or if you have a runway with double the normal length.

"even allow for luggage stowage by the crew during boarding" the actual idea was for passengers to load their own luggage. Flown on an Il-86 once in the USSR and that was exactly what we had to do, carry our luggage to the aircraft. But there was ground crew to make sure it was properly stowed, the idea of passengers loading their own suitcases had been partially abandoned shortly after the aircraft entered service.


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How safe is the Boeing 737-800 in high winds?
I'm not good with flying. However, on Wednesday morning I'm flying from Gatwick to Bergen, Norway, traveling alone with two young children.
I'm trying desperately to not show my kids how afraid I am of flying - with families in two countries we have to do this all the time. So I have to be mentally prepared for this: the forecast is showing high winds.
Around the time of take-off (10:50) it shows 16-18mps, SSW.
As far as I've been able to understand, this is at the limit of what a Boeing 737 can take?
Basically: Will we be safe? How can I know? Will it be bumpy? What will happen? Should we cancel?
Can you help me understand?

Comments are not for extended discussion; this conversation has been moved to chat.

BTW there is no guarantee that you will fly a 737-800. Airlines can swap planes as they see fit.

@e-d-huckerby - how was your flight? How's Norway?

"...it shows [winds] 16-18mps, SSW" - I don't believe that is considered high winds, but I could be mistaken. Strong cross-winds may be around 30 or 40 mph. Also the random cross-winds and wind shear are probably a bigger concern. For example, as far as I know Delta Airlines had one fatal crash and it was due to wind shear during landing in DFW.

@jww, assuming mps is metres/second, 18m/s is about 41mph. SSW is also a (not quite direct) crosswind at Gatwick.

Extremely safe.
Firstly, your pilots will have access to much more detailed and real-time weather information than you can get. They want to get home safely as much as you do, and will not fly if it is not safe to do so.
If the wind is coming from straight ahead, there is no maximum limit, which is good as aircraft takeoff and land into the wind whenever possible. If the wind is coming from the side - known as a crosswind - the limit in a 737 is about 36 knots/19 mps (the specific number can vary but that's a guide). The reason for this limit is to avoid the winnd blowing the plane off the side of the runway. So if the wind is that strong, hopefully the runway faces into wind, otherwise your pilot may have to delay the takeoff until it calms a bit.
Once the aircraft lifts off the ground, the wind speed is irrelevant (except for navigation purposes). Imagine a fast flowing river. Placing your canoe into the river when it is at such speed is difficult, but once you are in the middle of the water it is smooth as silk. The transition from ground to cruising altitude is similar. The initial climb will probably be turbulent but the aircraft is built to sustain more than nature can throw at it. Once at altitude the wind speed will almost certainly be much more than 100 knots - but just like the fast flowing  river, if you close your eyes it will feel nice and smooth.
You should only cancel your flights if you want to throw away your money. Otherwise just try to relax, and understand that many airline delays that you hear of are caused by a pilot choosing safety over schedule.

" from straight ahead, there is no maximum limit" well, you DO have Vne, though

@Federico Well I guess, but, context! If the wind alone will exceed Vne in a 737 humanity has much bigger problems than this flight!

Sure, it's that I like nitpicking :P

"Firstly, your pilots will have access to much more detailed and real-time weather information than you can get. They want to get home safely as much as you do, and will not fly if it is not safe to do so." Your pilots have families (of some sort) too and this very much applies to them!

@Federico I can only hope most pilots would not consider taking off while a tornado is passing over the runway :)

@mbrig Why? The 'storm chasers' seem to have pretty safe flights (I know that is not from take off but still)...

@Cloud because takeoff is different from level flight

"...and understand that most airline delays that you hear of are caused by a pilot choosing safety over schedule..." Citation?

@Federico For the benefit of the record - naive googling suggests that 737s don't actually have Vnes. Is that the case? If so, what's the correct concept, and what speed is it? (Assuming 'vanilla' conditions at sea level, obviously.) If not, what's the Vne?

More seriously, though - I feel that this answer underplays the role of wind gusts in both absolute safety as well as passenger comfort, which I imagine is a large factor in how bumpy the takeoff feels to passengers. Is there a way to estimate that from the weather forecasts?

@E.P. that's better taken to chat, since it deviates considerably from the topic in the question/answer. feel free to ping me in the hangar and I will answer there

@E.D.Huckerby Also, statistically it's less likely there will be a crosswind at takeout as airport runways are laid out to align with prevailing wind directions.

@T.J.Crowder well, most delays are due to 1) an aircraft defect, 2) unsafe weather, and 3) fatigue limits. In all cases the pilot is electing to take the safest course of action (even if the rules say they must - following the rules is still choosing the safest option!)

@E.P. that's because Vne would be well above speeds that make flying impossible due to other considerations most likely.

@Ben - That's what I'm asking for a citation for, as opposed to equipment or staff logistics/availability issues. Some equipment availability issues could probably be traced back to some safety decision along the way -- e.g., a knock-on effect -- but I'm curious if "most" delays can really be traced back to such decisions. Only mildly curiuos, though. :-)

@T.J Crowder - it is a really interesting question, maybe one you should ask separately ;) I confess I did not look at statistics, merely using my experience to reassure the OP (and yes I was including knock-on effects of safety decisions)

@Ben - Yeah. I'm not very active on this site at all, would that kind of question be on-topic and specific enough, etc.?

"They want to get home safely as much as you do..." -- This could stand alone as the simplest answer. It may also be easier to remember just this little bit when ones mind starts to panic.

@T.J.Crowder I was once delayed because my flight (Atlanta to New York) had been supplied an airplane prepped to fly to Munich, and they had to find a truck that could offload the extra fuel so the plane could take off safely. Looking at it one way, it was an equipment or logistics delay, but looking at it another way, the delay was caused by safety concerns.  To a certain extent everything that happens in commercial aviation is related to safety concerns.

@T.J.Crowder Yes, that kind of question about airline and ATC procedure and safety would be on-topic here. Airlines definitely keep track of these things, so the statistics are probably available somewhere/at some level.

Short version: yes, the plane can take it
The 737 — or any other plane — will not take off unless the wind is within safe limits for the aircraft type.
Long version: your question almost answered itself
Did you know that last year there was not even not one single airfare-paying passenger fatality? Keep this in mind for a while...
Now, you came here asking "Are these wind speeds within the safe limits of this aircraft type?" There are two answers to this: "Yes", or "No".
I want you to ponder the potential answer: "No, those wind speeds are not safe for the 737 to fly in, but they keep doing it anyway". Does that sound like a realistic answer to you? Do you honestly believe that this is the way flight operations are being conducted across the world? When reading it like this, I do not think that this is what you believe, am I right?
But let us toy with the idea for a while anyway. Assume this is true. What would that mean? Well if this was the case — that aircraft are permitted to take off in wind speeds they cannot really handle — you would be hearing about a lot more crashes than you do. Planes would be dropping to the ground left and right. It is inevitably so that — if the answer was that planes fly in winds they cannot handle — there would be more crashes.
But this is not something you hear about, because it does not happen: planes do not take off in winds they are not certified to be able to handle. Last year's record — with not a single fare-paying fatality — would not be possible if planes were allowed to take off into dangerous winds.
So it does not really matter what the weather prognosis says, because if — on the day of your travel — the winds are more than the plane can take, the flight will be cancelled.
This is not even mentioning the fact that the limits imposed on aircraft have a safety margin built into, so that even if winds do gust up a little bit more, the plane can still take it.
And if the weather at your destination has fouled up before you get there, well this is what the divert airport is for. The divert is a pre-planned backup airport that the flight can go to if things turn fouler than expected.
So in the end: yes, your plane will be able to take the winds that prevail on the day of your flight, guaranteed, because if there are worse winds than that, you will not be flying that day.

Compare that with car accident fatalities, which occur in almost every single county in every country within a year, usually much more than once. And the no airliner fatality statistic was for the whole planet!

There are quite a few fatal accidents on https://en.wikipedia.org/wiki/2018_in_aviation . Where did you get that stat from?

@RobinWhittleton Last year... 2017 was the safest year on record for commercial air travel.

Let us continue this discussion in chat.

On the plus side, when winds are high, birds are less likely to crash the plane into the Hudson!

@Kheldar That would be especially true on a flight from the UK to Norway. I imagine few such flights pass near either Hudson river or Hudson bay, thus reducing the risk to virtually zero even in the presence of birds and absence of high winds.

Haha indeed, but you get the point though ^^

As you can see on google maps Gatwick's runways are aligned (like many in the UK due to our prevailing winds) roughly east-west. In actual fact the runways are numbered 08 & 26 relating to 080 and 260 degrees respectively.
A wind coming from the SSW, for arguments sake, blow at roughly 200 degrees. Aircraft take off into wind, so you will invariably depart from runway 26. There is therefore a 60 degree difference between take off and wind direction (not exactly, but for illustration sake.)
18 m/s in roughly 35 knots, and if the whole of that wind speed was at exactly 90 degrees to the runway it might be close to the maximum, but it's not, only 60/90 of it is the "crosswind" component. When you calculate the numbers you would have roughly

30 knots crosswind
17 knots headwind.

Which is not close to the maximum.
Bergen airport is roughly north-south, but I imagine the weather there will be considerably different and I'll forgo the same illustration as above - suffice it to say the Pilot will not fly outside of his own and his aircraft's abilities. They always have the ability to divert, to wait out bad weather, or to turn back.
Relax, flying is statistically the safest way to travel.

If anyone is interested in the 'wind triangle' calculations used to calculate head and crosswinds, the formulae are HW= WS*cos(WD-RD) and XW= WS*sin(WD-RD) where HW is Headwind (negative result = tailwind), WS is Wind Speed in whatever units you want, WD is Wind Direction in radians and RD is Runway direction in radians. (Courtesy http://www.edwilliams.org/avform.htm#Xwind)

To give you a perspective of how safe commercial flying is, take a look at these two pictures:

Those are the B737-800 that are in flight at the moment of typing this (which is around midnight in UK, so not the busiest time of the day!). If you bother to count, you'll see that there are 1375 of them. And this happens at all times, every day of the year, no matter what the wind is.
If you want to see a more detailed view, or what all flights (and not just those with a B737-800) look like, go to Flight Radar 24.

Please relax, as much as you can.  The safety of your trip is the number one priority of the airline.  As far as 'bumps' are concerned, there are always possibilities of them occurring, but there is no aeronautical reason to be concerned.  Occasionally there are "bumps" in flight that will be uncomfortable, but very rarely injure the passengers belted in properly.
Have a good flight and I imagine the children will enjoy the experience for the first few minutes and then fall asleep.

The key there is "always wear your seat belt".  I've been in a 737 that dropped several thousand feet in about 3 seconds.  They had to emergency land.  The people who where not strapped in did not have a good day.

A crosswind during takeoff is no big deal, as long as it's below the airplane's limits.  The airplane starts off with all wheels solidly on the ground, which makes it easy to keep it pointed down the runway.
The demonstrated maximum crosswind for a 737-800 is either 33 or 36 knots, depending on the presence or absence of winglets on the wingtips.  An 18 m/s (35 knot) SSW wind at Gatwick runway 26 works out to a crosswind component of around 29 knots, well below the limit.
Keep in mind that this is a demonstrated maximum: Boeing has shown that the airplane can always take off or land safely with a wind of this strength.  The actual limit of what the plane can handle is higher (probably somewhere around 40 knots or so, given the sort of safety margins the airline industry favors).
What you're going to experience: the airplane will roll down the runway and take off, just like normal.  Once you're off the ground, you'll feel a bit of bumpiness as the airplane climbs up through the surface turbulence layer.  Once the wheels are up, the flaps are retracted, and you're a few hundred meters up, it should smooth out, and the flight will be no different from any other.

+1. Good answer that addresses the most important parts of the question and manages to omit irrational claims of "100%" safety. And no need to cite incident lists that are bound to make everyone nervous.

Prefix - I don't recommend you read the link to this source as it lists worst case scenario events (imagine you wanted to take up soccer and were researching the safety of the sport by searching for "worst ever soccer injuries", you would never take the usually very safe sport up, it is a terrible method for research).
Anyway, to summarize for you - from the list of incidents and accidents on the 737-800 type over the last 10 years, according to Wiki:

Only 1 European airspace provider (Ryan Air) had an incident. there were no fatalities or even serious injuries.
Almost all of the other incidents involved no serious injuries
As usual, the ones involving fatalities were from Eastern airlines. Examples: Air India Express, FlyDubai, Turkish Airlines (OK not Eastern, but still not European) and China Airlines. I don't know what these guys do differently but between their incident lists and disappearing aircraft, I think I'll take the train to the East).

Many European airlines (EasyJet, Ryan Air, KLM) have 0% fatalities and have been operating for over 30 years with this type and others that are very similar.
I know I didn't directly answer your question about wind speeds, but that is because I do not need to and others have done so for you. It doesn't matter - the pilot will 100% not fly if he has even any idea that doing so will be unsafe.
Now, let's say that you are super unlucky, you are on one of the very, very, very rare flights that has an incident (let's say it's due to crosswinds, as you fear) - what is the likely outcome? A delay in your travels and a bump. 99% of all incidents involving jet aircraft do not involve fatalities.
If you do read through the incident list of any type, most of them will be hard landing, bird strikes etc. that usually involve emergency landings, with all of the passengers calmly leaving the aircraft with nothing more than a couple of bumps.
If none of this helped, take a fear of flying course - they are fantastic and will probably eliminate your fears.

FYI Turkey is considered transcontinental (like Russia); part of it is in Europe. Also, I think the discriminatory remarks really don't belong in the answer as they're not only unfounded and offensive but also unrelated to the subject at hand ('is a 737-800 safe/smooth in these high winds').

@TylerH Not unfounded, the discourse was based off of the incident records of the stated airlines, many of which are banned in European airspace.. I think that speaks for itself.

Everyone has given you some great answers; including how runways work and how safety is a primary concern.
You should also know, in addition to all that has states, pilots often ask pilots of other aircraft that are flying in the same direction for condition reports. These are to make sure that any unexpected turbulence (a disturbance in the air) can be avoided.
Pilots will also often change and adjust their routes to avoid areas of turbulence; everyone prefers a smooth flight - especially the pilots.
Technology helps a lot, and weather radar is getting better constantly. However, it is still not perfect - which is why despite all the technology, advanced reports, weather analysis and precautions - pilots still rely on other pilots flying to give them an idea of what the actual air feels like for them, to avoid any unpleasant bumps.
So, you should rest assured that everything is working towards giving you a smooth ride.
Relax and enjoy your flight.


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Are these ballast bags for a hot air balloon?
While driving around on the back side of Aspen Mountain (so up around 10,000 feet altitude) we came upon these bags of ash.  They look like they could be opened up on the bottom to let the contents out, our best guess is that they are ballast bags for a hot air balloon.  You can see my brother's legs in the first picture for some kind of scale.
Were we right?

I don't know how much ballast a hot air balloon might need, but those look like what are known here in Australia as "Bulka-Bags". They are used for a huge variety of granular products, from sand & fertiliser to grain, or any other usually dry powder product. They usually carry a cubic metre or so, and maybe a tonne of mass. Too big for a balloon, perhaps they were jettisoned by a helicopter carrying them underslung due to bad conditions? https://www.brisbanebags.com.au/Bulk-Bags?gclid=CjwKCAjw-dXaBRAEEiwAbwCi5utg3LR5aX76awl1Uod4UvxJI8tlbPNyV97noJ2qUx1Dsh4m_Q8O6xoC8OYQAvD_BwE

@Mackk I'm not sure that they are Bulka-Bags as they look like this

Also, by the looks of the pictures, the material does not seem like a Bulka-Bag material nor a Ballast Bag material

The contents felt like ash to me.

@BettyCrokker It's not ash (that would be gray), it's likely charcoal from incompletely burnt branches.

@FallenUser apart from the colour, to me they look like those, laid on the side

OK, so we've got this: https://www.buyactivatedcharcoal.com/super-sack-specials.html

In Alaska and the Canadian Yukon charcoal or ash is sometimes used in "bomb" drops to melt ice on rivers and creeks that have ice dams. However I have never heard of helicopters used for this though it is conceivable there might be a beneficial ranching operation or homes endanger of flooding. I seem to remember the last WWII A26 bomber used for this being retired from service about 20 years ago and they would have replaced it with something. It usually used coal dust. Now there are probably legal problems with interfering with nature.

Almost definitely not.
Hot air balloons control their height by changing their temperature, they don't typically use ballast bags. It's possible that these were ballast bags on a gas balloon, but ash seems like a strange choice for weight considering how light it is.


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Is a ducted fan considered a jet or propeller for the performance parameters?
Right now I am working on a UAV design which will use ducted fan. But the performance calculations are a bit troublesome. For some calculations jet and propeller results are almost same but for the parameters like takeoff, landing, endurance and much more T/W and P/W results doesn't make any sense.
For example, T/W takeoff (according to Sadraey's approach) with jet assumption is higher than my max T/W but P/W takeoff (according to Sadraey's approach)with propeller assumption is one third of my max P/W (When calculating P/W, I directly summed engine powers and divided by weight, I am not sure about is either because I didn't involved any efficiency or altitude effect) and in previous studies, I found that I would takeoff with %86 of my max power not one third of my max.
Should ducted fan considered as jet or propeller for the performance parameters?

They are most definitely propellers.

Sir, thank you for the information. I know that propeller efficiency changes from one to another but do you have any suggestion for 12.5 cm diameter, 30 N thrust generating and 1665 W power ducted fan ?

@J.Brown, could you perhaps show the exact calculations you performed? It would also be helpful if you showed the exact reference of the book you used.

Performance textbooks classify prop vs. jet based on whether the propulsion system is considered 'thrust producing' or 'power producing'.
Whether a propulsor is thrust or power producing is based on two factors.
Is the thrust (or power) available roughly constant with velocity?
Is the fuel consumption roughly proportional to thrust (or power)?
An idealized jet is a thrust producing engine.  The textbook assumptions say that a jet's thrust available is constant with velocity and the fuel consumption is $\dot{W}=\mathrm{TSFC}\,F_n$, where $\mathrm{TSFC}$ is the thrust specific fuel consumption.
An idealized prop is a power producing engine.  The textbook assumptions say that a prop's power available is constant with velocity and the fuel consumption is $\dot{W}=\mathrm{BSFC}\,P_{shaft}$, where $\mathrm{BSFC}$ is the brake power specific fuel consumption.
In reality, these idealizations are never true.  Serious aircraft performance modeling requires a more sophisticated propulsion model and these concepts of 'thrust producing' and 'power producing' are not very useful.  The approximations that result (such as best climb, endurance, range -- at best CL/CD, CL^1/2/CD, or CL^3/2/CD) are not very accurate.  Similarly for the Breguet Range equations for prop and jet aircraft.  Unfortunately, most of the textbooks that present these approximations never discuss the reality of propulsion and the deficiencies required to write these simplifications.
The design of a duct for a fan has profound impact on the performance of the fan.  High speed aircraft (cruising at M=0.8 and above) will have a duct shaped such that when the flow reaches the fan front face, it is substantially slower than freestream (say M=0.6).  This helps keep the fan tip speed down and allows the engine to operate at high speeds.  This kind of fan actually reduces static thrust.  These ducts typically have an exit area smaller than the fan area.
Ducts can also be designed to maximize static thrust.  These fans actually accelerate the flow from freestream to the fan face.  Though they are unsuitable for high speed flight, they are great at static thrust. These ducts typically have an exit area equal to or greater than the fan area.
Duct performance behavior also depends on how you're driving it -- a gas turbine, a piston engine, or an electric motor.  And how the limits on that device are enforced.  For example, an electric motor and drive will have certain RPM (bus voltage and throttle) and torque limits (current).
In a sophisticated system, these will be monitored and kept within safe limits by an active control system.  In a hobby-grade system, the battery bus voltage drops without control, the speed controller has a 100% throttle, and the controller may limit current -- or perhaps a fuse is the only limit you have.  Sometimes, the only limit is by choosing a prop that won't overload or allow the system to over-speed.
My recommendation is to take a step deeper in your calculations and develop an off-design engine deck for your propulsor.
If you are designing a high-speed fan like that used on a transport aircraft, you will start with a traditional turbomachinery fan map.
If you are designing a low-speed fan that will not operate into compressibility, then I would recommend you use Prof. Drela's DFDC.  Esotec is a company that claims to have an improved version.
Next, you are going to need a model of the device producing shaft power -- turbine, piston, or electric.  Importantly, what are the limits -- max torque, max power, max speed -- these will form an envelope of what is allowed.  Ideally, you will also have some measure of efficiency or fuel consumption within those limits.
Finally, you need to couple the two together -- match the torque and speed required to spin the propulsor with the operating torque and speed of the driving machine.  Keep the machine within safe operating limits, move the propulsor around in the flight envelope (speed, altitude, throttle).
This paper gives an example of this for a high speed fan driven by an electric motor.

is a ducted fan considered a jet or a propeller?

Well, is a jet considered a reciprocating engine or a rocket?

Does it matter at all what you call it?

First, the commonality is that both reciprocating engines and turbines produce mechanical rotational force to do work: that is to run their compressors, oil pumps, fuel pumps, create electricity, what ever needs to be done to keep the engine and aircraft systems running.
Early jets relied on expulsion of hot gasses to create thrust, using the mechanical force of the turbine to turn the air compressor.
Reciprocating engines create thrust by turning a propeller, and use the mechanical force of the pistons to also intake air (compresser optional).
The job of the turbine is the same as the job of the piston for incoming air, spark, and fuel, but what about propulsion?

can a turbine turn a propeller?

Of course! They are called turboprops.  Can a turbine turn a fan?  These are fan jets.
Which brings us to the ducted fan, powered by ... an electric motor?
Electric motors do not use hot gasses from combustion to produce mechanical force or thrust, so it can't be a turbine or a reciprocating engine.  It's ... an electromagnetic engine.

no matter how mechanical energy is produced, fans function as propellers

They are subject to the same benefits and limitations as propellers.
Ducted fans improve propulsive efficiency at low airspeeds compared to unducted propellers.
Running the numbers on your ducted fan:
1665 W = 1.665 kW = 2.23 horsepower
12.5 cm diameter prop = around 5 inches
30 N = 6.7 lb force of thrust
Not bad, really.  Can we do better for lifting?

fewer, longer, slower blades

That is the approach the designers of this aircraft took.
For the amount of horsepower you have, at low airspeeds, a 12 inch propeller may be more efficient at generating thrust.

As a rule of thumb, for a ducted propeller you can consider a thrust increase of 30% in respect to an open propeller, the power being equal. This should give you a reasonable value to start with.

That depends very much on the duct in question. If the duct design is bad, you will loose thrust.

@U_flow: oh well, also the propeller if it's bad designed is going to generate drag instead of thrust ;-). But I think this is not the point here...

that is true, but for duct design it is apparently especially easy


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Input Parameters for Combustion Chamber
I am doing a column breakup study. But for a better study I need air velocity, turbulence intensity (not primarily needed though),temperature, pressure and same parameter for injected liquid fuel. I searched for an commercials but there is no useful information. Could you help me with the sources ?
Thank you in advance.

Engineering or chemistry stackexchange may be better place for your question

I've posted it. Thank you


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What is the official term for a gas / petrol station for planes?
I'm talking specifically about small airports where they don't have the fancy equipment and they actually have to go to a specific place to refuel for example cars go to gas station / petrol station so:
Is there an official term for a fuel station specific to planes?

In some places, it's simply the Kwik Stop

Official? Per whose office?

At airport with a standalone self-serve facility, it's a Self Serve Fuel(ing) Station.  If it's a business selling fuel in addition to other services, that is a Fixed Base Operator, or FBO.

On a small GA airfield we just refer to them as "The pumps". As in my typical radio conversation goes like this

[Airfield] [service], G-ABCD request taxi to pumps.

They’re referred to as self service fuel pumps, or fuel terminals.  I don’t know if anybody has officially named the but pilots call them that.

Our fuel pumps are on the west side of the airport and most people just request: “Taxi to west-side fuel.”


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smartphones in fligth mode when bad weather conditions?
when flying form Vienna to Stuttgart, we had a terrible weather conditions, before landing the cabin crew announced that by request of the captain, all electronic devices must be switch off, not allowing even their use in flight mode..
any particular reason for that??
maybe avoiding the selfie effect by millenials if something goes wrong by landing??
thanks is advance

What exactly do you mean by "terrible weather conditions"? Turbulence, strong winds or thunderstorms? Or low visibility, which might have required a CAT II or III ILS autoland? Also, which aircraft were you flying in?

Related: Instrument landing: why do all electronic devices need to be shut off?

it was pretty windy up in the air and when landing it was  very foggy..

it would be better if you would tell us the flight number and day of flight. "pretty windy" does not help much in understanding the conditions

EW 2757, yesterday 8:55 pm


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can I do my PPLA license in spain even if I live in Germany?
I live in Germany but I was born in Spain, I wpuld like as a hobby, to get my PPLA license..
but I would like to do that in Spain, if so, can I still flight in germany?
is that possible?
Thanks..

Yes, an EASA PPL is valid in all EASA member states

Could you add some sources to back up your answer?